Method of preparing ferritic iron powder for manufacturing shaped iron bodies



Dec. 29, I942. P. SCHWARZKOPF 2,306,665

METHOD OF PREPARING FERRITIC IRON POWDER FOR MANUFACTURING SHAPED IRON BODIES Filed March 19, 1941 INVENTOR ATTO RN EY atented Dec. 29, 1942 Mn'rrroln or r'aarsnmc raam'rro mow rownna ron MANUFACTURING swan IRON BODIES Paul Schwarzkopf, Yonkers, N. Y., asslgnor to American Electro Metal Corpo ation, Yonkers, N. Y., a corporation of Maryland Application March '19, 1941, Serial No. 384,0'i8

6 Claims.

This invention relates to the production of shaped sintered iron bodies of desired carbon content, particularly but not exclusively of the character of steel or alloy steel, from'powdery initial material.

The invention is particularly concerned with a process of manufacturing shaped iron bodies of predetermined content of combined carbon and other admixtures, if desired, of the character of steel or alloy steel as described in the copending applications of C. G. Goet'zeL'Ser. No. 364,814 and Renzo U. Volterra, Ser. No. 364,797, according to which about to 70% ferritic or pure iron powder are intimately and uniformly admixed with normally not briquettable powder of an iron compound and, if desired, other admixtures, this initial mix compacted under pressure into a coherent body of desired shape and thereafter subjected to heat treatment including a final sintering step between about 1150 C. to 1390 C. until a dense and strong body is obtained- If somewhat porous bodies are to be made, lower final sintering temperatures, above 900C. and preferably above 1000 C. can be employed.

Compounds of iron powder mentioned above comprise iron oxide, 1. e. an oxygen compound of iron which is available in the market at low price either as recovered from the ores or as mill scrap. Such compounds also comprise iron containing carbon, such as steel consisting of iron and about 0.1% to 1.7% combined carbon, and cast iron (white and gray iron) containing about 2% and more combined carbon. Such steel powder may also contain desired admixtures as usual in alloy steel, e. g. tungsten, molybdenum, tantalum, vanadium, titanium, silicon, nickel, cobalt, chromium, phosphorus and/or manganese. desirable admixtures of the type just mentioned, and if some of them are present as undesired impurities, the cast iron should be purified before it is powdered.

It is well known that powders of iron oxide, steel, alloy steel and cast iron of the types referred to are either not briquettable at all or only under excessively high pressures which canafter and in the appended claims "normally not briquettable."

Any desired admixture referred to above may either be contained in the initial steel or cast iron powder or added to the initial mixture either as individual metal or in the form of an v alloy as obtainable in the market. Such alloys are for instance ferronickel, ferrochrome, ferromanganese, ferromolybdenum, stainless steel scrap, ferrosilicon, ferrotitanium, ferrovanadium, ferrotungsten.

These alloys, if powdered, are also normally not briquettable in the sense defined above.

To those normally non-briquettable powders, ferritic or pure iron powder is admixed in suitable amounts as a binder. This type of. iron is briquettable under low pressure and renders the initial mixture briquettable undercommercial pressures. However it is obtained, either by careful chemical treatment and particularly deoxidation of iron oxide, as pure sponge iron, etc., it has the drawback of being very voluminous, i. e. the loading weight of the powder is rela- ';tively small and mostly about 1.5 gr./cc. The

loading weight of the non-briquettable powders of iron compounds of the type referred to is,

,- however, far higher; thus e. g. steel powder has a loading weight of about 3 to 3.5 gr./cc. By admixing such non-briquettable powder of great loading weight with ferritic or pure iron powder of low loading weight, a powdery mix results which is mostly still of undesired small loading Such cast iron may also contain weight because for commercial production of shaped bodies by sintering of powdery ferrous initial material, minimum loading weights of 2.4 to 2.5 gr./cc. are desired.

From the above it will'be appreciated that many factors are to be considered in composing the initial mixture; (1) The proportion of ferritic and non-ferritic iron and other admixtures should be such that upon final sintering a body of desired composition results; (2) the ferritic iron should be present in sumciently large amount that pressing to shape of the mix into coherent bodies is possible at commercial pressures; (3) because of its high price, the relative not be used in commercial production. In the amount of the ferritic iron should be, however, as small as possible; and (4) the loading weight of the mix should be within a range securing commercial production.

It is an object of the invention to produce shaped sintered iron bodies containing carbon and/or other admixtures in a predetermined amount, in a more economical and emcient way than heretofore.

It is a further object of the invention to improve the production of shaped sintered iron bodies of desired density and predetermined average carbon content from two or more kinds of iron powders of different carbon content and at least one of which is normally, i. e. under commercially practicable pressures not briquettable.

It is a further object of the invention to produce by commercially practicable pressures and sintering, shaped bodies from "two or more kinds of iron powder, one of which is substantially pure iron or ferritic in character, while at least one other forms a. carbon containing iron or steel or an alloy thereof, which is normally not briquettable, and to consolidate them into a heterogeneous body of desired average carbon content, desired density and mechanical and/or thermal properties.

It is still a further object of the invention to produce under commercially practicable pressures and by sintering, shaped iron bodies from two or more kinds of powders, one of which consists substantially of pure iron or ferrite, while the other one, or others, are normally not briquettable and consist of any other kind of carbon and, if desired, other additions containing iron, and wherein the pure or ferritic iron serves as a binder for the other kind or kinds of iron for shaping under pressure.

It is a particular object of the invention to increase the loading weight of mixtures of ferritic iron powder and normally non-briquettable powders of iron compounds and other admixtures, if desired, by increasing the density of the ferritic powder particles to desired or predetermined extent.

These and other objects of the invention will be more clearly understood when th specification proceeds with reference to the drawing in which Fig. 1 shows diagrammatically a system for powdering, densifying or compacting, powdering again and sieving ferritic iron, and Fig. 2 shows in front elevation and Fig. 3 in side elevation a shearing r crushing mill for producing ferritic powder of desired or predetermined average particle size.

In order to increase the loading weight of mixture of ferritic iron powder and non-briquettable powders of the type referred to, according to the invention the initially voluminous ferritic powder is compacted and powdered again before it is admixed to the non-briquettable powder. The compacting and powdering steps may be repeated until a ferritic powder of desired higher loading weight is obtained.

It will be appreciated that low and high carbon steel, alloy steel, cast iron and iron alloys, such as ferro-nickel, etc., are all obtained by a process including a casting step, and the solidified body and powder particles obtained therefrom are therefore of highest density possible. Sponge iron is however very porous as indicated by its name, and ferritic iron obtained by any chemical process is due to the latter of great porosity also. Electrolytic iron is manufactured by depositing thin layers of pure iron one onto the other and therefore extremely porous. Therefore, ferritic iron, as available in commercial processes heretofore known, is necessarily more porous and of lower density than any material obtained by a process including a casting step, and so are the powder particles obtained therefrom. While, however, all kinds of steel, cast iron, and iron oxide are non-briquettable, ferritic iron is soft and malleable, however it may be obtained, and retains this property also upon being densified according to the invention. Therefore, if once or repeatedly compacted and powdered again ferritic iron is according to the invention admixed to nonbriquettable powder of an iron compound of the type referred to, the mixture is rendered briquettable. The amount of densified ferritic powder admixed depends upon the particle size and composition of the non-briquettable powder as well as the type of the final product to be obtained. In this respect, reference is made to the above mentioned copending applications stating in more detail the sizes of the powders and their relative proportions. As a general rule, 5% to 70% by weight of the desified ferritic powder may be used.

Apart from the fact that a ferritic iron powder desified according to the invention increases the loading weight of the initial mixture to desired extent and thereby the efliciency and economy of the subsequent compacting and sintering process, the further advantage is obtained that the relative amounts of ferritic andpther constituents of the initial mixture can be more freely chosen with respect to the desired ultimate chemical composition and metallurgical structur of the final body.

Th initial ferritic iron may be sponge iron if available in desired purity and at low price, or pure electrolytic iron. It may also be produced from iron oxide in well known processes and particularly in the one described in my copending application Ser. No. 349,996.

A preferably continuous process in which ferritic iron is obtained from iron oxide and thereafter subjected to the process according to the invention for comminuting and compacting it in order to increase its loading weight, will now be described with reference to the drawing.

Referring to Fig. 1, there a furnace is shown consisting of a tube 26 of high temperature resisting material, such as steel, Nicrome, tungsten, molybdenum or an alloy thereof, embedded over a part of its length in a refractory casing 21. Wires, bands or foils 2B of resistant material, such as "Nicrome, molybdenum or tungsten are arranged within that refractory 21 and wound around and close to tube 26 and are heated in adjustable manner by electrical current to a desired temperature. Another part of tub 26 is covered by a cooling jacket 29 such as of iron, which is passed by a suitable cooling medium. Through tube 26 a belt 30 preferably of molybdenum sheathing is passed over guiding rollers 3|, 32, 33 and a roller 36 which is power driven at adjustable speed in a' way not shown, e. g. by an electromotor of adjustable speed.

A hopper 35 provided with a gate 36 is arranged over a part of belt 30 in front of tube 26 outside furnace 21, and iron oxide powder 31 is filled into the hopper above the gate. Upon withdrawing of gate 36 for a predetermined period of time, a predetermined amount of iron oxide powder is fed upon belt 30 which moves with predetermined speed in the direction of arrow 39. After that amount of iron oxide powder has been deposited in a flat pile 38 upon'the moving belt, gate 36 is closed for a short period of time, and upon its reopening another pile 38 of iron oxide is fed upon the moving belt 30. Alternate opening and closing of the gate can be brought about manually or automatically, e. g. by a suitable cam drive (not shown).

The entrance of tube 26 is covered by a hood it through which the feeding outlet of hopper -hood which for this vided with apiston 51 45 passes airtightly. Belt 34- passes as airtightly as possible through a slit in that purpose may be pro vided with a packing e. g. of asbestos. At the outlet end of tube 26 a wall 4 Us provided having an opening 42 sufficiently large to allow belt 30 and the deoxidized iron cakes formed thereon to pass through.

Hydrogen under suitable surpressure is admitted through tube 43 intohood 40, passes tube 26 and escapes through opening 42 where it may be burned off.

Thus, piles 38 are deposited upon and moved on and with belt 30 through tube 26 and first exposed to high temperatures preferably between about 1000? to 1200 C. and thereby deoxidized, as described above, and eventually fritted into cakes 44 which are cooled and solidified while travelling through the cooling zone within jacket 29. By properly adjusting the speed of belt 30 with respect to a given length of tube '26 and particularly its heating zone, any desired period of treatment of the oxide while travelling through the furnace can be allotted.

Each cake 44 thus resulting from each pile 38 is eventually discharged from belt 30 when it passes roller 32 into a hopper 45 and between a pair of shearing crushers 46 of the type described with reference to Figs. 2 and 3.

Hopper 45 continues into a casing 41 which continues into a movable discharge end or chute 44 which can be rocked on pinions 49 from the position shown in full lines into that shown in dotted lines. This movable chute 48 is also provided with a curved plate or gate which, upon turning the chute into the position shown in dotted lines, closes the lower end of casing 41; Rocking oi chute 48 into one and the other position can be effected manually or by automatic means (not shown), e. g. by a cam drive.

Below the discharge end of chute 48 a die is arranged consisting of a portion 5| provided with a cylindrical or rectangular space or bore 52 and closed at its bottom by means of a strong slide 53. The die may be heated by conventional electrical means or a hot flame (not shown) if operation at temperatures above room temperature is desired. A protective atmosphere is to be applied if the elevated operation temperatures be close to or above oxidation temperature of the ferritic iron.

It will be appreciated that the ferrite powder 54 produced by pulverizing cakes 44 by means of crushers 45, will either fall through the lower part of casing 41 and chute 48 in its position shown in full lines, into bore 52 of die 5|, or pile up in the lower space of casing 47 above gate 50 when the chute 48 is swung into the position shown in dotted lines and thereby plate or gate 50 into its position for closing the lower end of casing 41.

Thus powder 54 will be filled into space 52 in predetermined amount while slide 53 is in the position shown; thereafter chute 48 will be rocked or swung into the position shown in dotted lines.

A pressing block ,55 mounted on rod 56 prowithin a pressure cylinder 54, will now be lowered and enter space 52, compressing therein the soft ferrite powder and agglomerating it into a coherent and quite dense lump. Pressures of about 5 to 25 tons per sq. inch and more may be thus applied upon the powder within space 52.

asoaees mill 45, 45 the same way For lowering pressure block 55 a fluid under pressure from a source not shown is admitted into cylinder 58 above piston 51 through a threeway-valve 59, while a fluid below piston 51 is allowed to escape through a three-way-valve 60. After the compression of the powder in die Si is completed, pressure fluid from a source not shown is admitted through valve 60 below piston 51 while the fluid under high pressure is cut off and released, respectively, from the space of cylinder 58 above piston 51 through valve 59;

The compressed and coherent ferrite lump is now releasedfrom die 52 by moving slide 53 to the left manually or automatically and the lump 6| falls between crushers 62 arranged within a casing 63 and is powderized again. The powder 64 thus obtained consists of substantially more dense particles than the ferrite powder 54,'and is discharged upon a vibrating sieve 65 of desired mesh. The sieved powder 66 is either discharged in a storage vessel 61 compression, crushing and sieving.

It is understood, that opening and closing of gates 36 and 50, and of slide 53, and rotating of valves 59, 60 into one or the other position can be eifected automatically by well known adjustable timing devices.

It should be further understood that the powder 54 derived from crusher 46 can either be discharged upon sieve 65 directly, if its average fineness is satisfactory, or delivered through chute 48 directly to crushers 62, if its particle sizes are further to be reduced.

In Figs. 2 and 3 a crusher is shown adapted to pulverize in a shearing action a cake of ferrite obtained in the way described. The crusher consists of two rolls each comprising a cylindrical portion I0, II provided with a number of equidistant flanges or collars l2, I3 of equal width. The distance between the adjacent flanges I2 is such that a flange I3 can enter between them, leaving a clearance between their opposite side faces corresponding to the particle size desired. Trunnions l4, I5 provided on both sides of the cylindrical portions H), II are journalled in bearings I6, I! the distance of which can be adjusted so that the distances of the cylindrical circumferences of flanges I2 from the cylindrical circumference of the cylindrical portion II and the distances of the circumferences of flanges l3 from those of cylindrical portion l0 equal the clearance between the lateral juxtaposed surfaces of the flanges l2 and I3.

On one of the trunnions l4, l5 each, gears l8, 49 are mounted which mesh third gear 20 which is mounted on shaft 2| which is power driven with adjustable speed in any convenient way (not shown), e. g. by an electromotor of adjustable speed.

In operation, a cake 22 fed in the direction of arrows 24, 25, will be drawn between the flanges -12, l3 and cylindrical portions IO, U and thereby crushed by shearing action.

It will be appreciated that instead of combining a process of recovering ferritic iron in the form of cakes or lumps and comminuting, compacting and comminuting it again, lumps of ferritic iron, such as pure duced sponge iron can be fed into the crushing as the'cakes 44, and in the furnace for reducing the iron oxide and compacting it simultaneously into (:0-

herent cakes can be omitted in the process illustrated in Fig. l.

or subjected to repeated crushing and sieving action, or even to repeated electrolytic iron or re- It is also understood able in powdery form, can be ieddirectly into chute MB of Fig. 1 inorder to compact it and to increase the loading weight of the resulting powder, and in such event both the furnace as well as the crushers 46 can be omitted.

It is further understood, that the compacting and powdering steps shown in Fig. 1 can be repeated in that the powder produced by the crusher mill 62, 82 is not fed upon a sieve but in a chute of another compacting and powdering mechanism similar to that shown in Fig. 1, and such compacting and powdering steps may be repeated until powder particles densified to predetermined extent and of desired average size are obtained, ready for sieving.

It should be understood that the invention is not limited to the exemplifications herein shown but to be derived in from the appended claims.

What I claim is:

1. In a method of preparing a ierritic iron powder, in particular for admixture with other powdery components such as normally nonbriquettable iron compounds, the steps of subjecting powdery and porous ferritic iron at least its broadest aspects that ferritic iron if availous powder of predetermined density and average size of its particles is obtained.

4. In a method of preparing a ferritic iron powder, in particular for admixture with other powdery components, such as normally nonbriquettable irun compounds, the steps of agonce to a cycle of treatment comprising mechanically compacting and thereby agglomerating in to a coherent porous cake and densifying said ferritic iron and comminuting it thereafter, until a briquettable powder of predetermined density and average size of its particles is obtained.

2. In a method of preparing a ferritic iron powder, in particular for admixture with other powdery components, such as normally nonbriqu'ettable iron compounds, the steps of comminuting spongy lumps of ferritic iron mechanically compacting at room temperature and thereby agglomerating into a coherent porous cake and densifying the powder thus obtained, and thereafter comminuting again the compacts thus produced, until a briquettable powder of predetermined density and average size of its particles is obtained.

3. In a method of preparing a ferritic iron powder, in particular for admixture with other powdery components, such as normally nonbriquettable iron compounds, the steps of comminuting by shearing action spongy lumps of ferritic iron, mechanically compacting under pressure the powder thus obtained agglomerating into a coherent porous cake and comminutingagain by shearing action the compacts thus produced, until a briquettable still somewhat porglomerating in the heat between about 1000 to 1200 C. into a coherent porous cake and cooling porous ferritic iron pieces, comminuting the agglomerated porous lumps thus produced. and subjecting'said comminuted ierritic iron at least once to a cycle of treatment comprising compacting under pressure said comminuted iron and thereafter comminuting again the compacts thus produced, until a briquettable, still somewhat porous powder of predetermined density and average sizeof its particles is obtained.

5. In a method of preparing a ferritic iron powder of predetermined loading weight, in particular for admixture with other powdery components, such as normally non-briquettable iron compounds, the steps of subjecting powdery and porous ferritic iron at least once to a cycle of treatment comprising mechanically compacting at room temperature and thereby agglomeratinginto a coherent porous cake and densifying said ferritic iron and commlnuting thereafter the compactsthus produced, until a briquettable powder of predetermined density of its particles and loading weight is obtained.

6. In a method of preparing a mixture of powders of ferritic iron and normally nonbriquettable components, such as iron compounds the production of which includes a casting step, of predetermined loading weight for compacting under pressure and sintering into shaped bodies of predetermined chemical composition, the steps of subjecting porous ferritic iron at least once to a cycle of treatment comprising mechanically compacting and thereby agglomerating into a coherent porous cake and densifying said ferrltic iron and comminuting thereafter the compacts thus'produced until a briquettable, still somewhat porous final powder of predetermined average size of its particles is obtained, and admixing said final powder in such a ratio with other powdery components at least a substantial part of which is normally nonbriquettable and includes iron compounds, that the resulting mixture has a predetermined loading weight and the final body obtained therefrom upon compacting and sintering is of predetermined chemical composition.

PAUL SCHWARZKOPF.

CERTIFICATE' OF CORRECTION. Patent No. 2,506,665. D cemb r 29, 1%.2.

PAUL SCHWARZKQPF.

It is hereby certifiedfthat error appears in the printed specification of the above numbered patent requiring correction as follows: Page L first column, line 21,, claim 1, after "components", line 58, claim 2, after iron and line 52, claim 5, after "obtained" insert a comma; and that the said Letters Patent should be read 'with this correction therein that the same may conform to the record of the case in the Patent Office Signed and sealed this 2nd day of March, A. D. 1915.

Henry Van Arsdale,

(Seal) I Acting Commissioner of Patents CERTIFICATE OF CORRECTION. Patent No. 2,506,665. December 29, 19h2.

PAUL SCHWARZKOPF.

It is hereby certifiedfthat error appears in the printed specification of the above numbered patent requiring correction as follows: Page )4, first column, line 21;, claim 1 after "components", line 58, claim 2, after iron and line 52, claim 5, after "obtained" insert a comma; and that the said Letters Patent should be read-with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 2nd day of March, A. D. i915.

Y Y 7 Henry Van Arsdale, (Seal) I Acting Commissioner of Patents 

